Pregnancy rates after cervical transfer of biopsied bovine embryos

THERIOGENOLOGY PREGNANCY RATES AF?ER CERVICAL TVNSFER OF BIOPSjED BOVINE YBRYOS M. Nibart , F. MechekouS , R. ProcureurI, 8. Chesne , D. Chupin and M. Thibier 1 IJNCEIA- 13, rue Jouet 6.P. 65 - 94703 MAISONS-ALFORT-France 2 INM - NOUZILLY - 37380 MONNAIE - France 3 INRA - Domaine de Vilvert - 78350 JOUY EN JOSAS - France Sexing bovine embryos using a Y chromosome-specific DNA probe (Theriogenology 27,248) requires preliminary biopsy of the embryo (i.e.. approximately 10 cells sampled from the embryo). The aim of this study was to assess the conception rates (C.R.) following biopsy and mock sexing of embryos that were then maintained 3 h at 20°C (group l), 24 h at 0°C (group 2) or deep frozen (-196"C, group 3). Seventythree embryos were studied of which 44 were collected on day 7 (blastocysts) and 29 on day 8 (expanded blastocysts; day 0 = dayT;fe They all had intact zonae pellucidae and graded 1. estrus). biopsy procedure was as follows: the collected embryos were placed in modified PBS medium and held by a micropipette. Ten trophoblastic cells were cut out using a microblade under a microscope (x 100) and with the aid of micromanipulators (Leitz). The embryos were then put in French straws (0.25 ml; IMV-Cassou) in modified PBS medium (+ 10% glycerol for deep-frozen embryos). All 73 embryos were transferred nonsurgically to virgin heifers after examination and without selection. The overall average C.R. was 44%. The C.R. appeared lower for the deep-frozen embryos collected on day 8, but differences were not significant (P>O.O5).

Group 1 (20°C) 2 (0°C) 3 (deep frozen)

No. 15 7 22

Day 7

C.R.

No.

53% 56% 41%

/ 17 12

Day 8

C.R.

Mean C.R.

/ 53% 17%

53% 54% 32%

Conception rates over 50% were recorded for fresh and cooled embryos and were close to those routinely recorded in the field for intact embryos (approximately 60%). This would suggest that if sexing requires less than 24 h, there would be no adverse effects of cooling embryos compared to using fresh ones. Similarly, the trend observed here is that if deep freezing is necessary, it would seem advisable to collect blastocysts rather than expanded blastocysts.

234

JANUARY1989VOL.31NO.l